Application of Electron Shuttles in the Remediation of Cr(VI)-Contaminated Wastewater: A Short Review

As one of the most leading heavy metals which primarily originated from extensive anthropogenic activities, Cr(VI) poses tremendous risks to environmental safety. The microbial remediation of Cr(VI)-contaminated wastewaters emerged as a promising approach on account of its economic and environmental benefits. Electron shuttle (ES) is a category of compounds, which is able to mediate extracellular electron transfer ascribed to its stable and reversible electrochemical behavior. They could be naturally produced, artificially synthesized, or bacterially secreted, and the addition of ES promotes the removal performance of C(VI)-contaminated wastewater by improving redox activity. The application of ES could mediate the long-distance transformation of electrons, providing a great impetus to the bioremediation of Cr(VI)-contaminated wastewater. In this paper, the influences of three typical ESs involving humic acid, quinones, and biochar on Cr(VI) removals were summarized, the main influence factors were described, and the application of ES in the management of Cr(VI)-contaminated wastewater are emphatically introduced.